When to replace timing chain?

joetiii · joetiii's Garage

I've got Wayne's book and plan on doing the Pressure fed tensioner upgrade soon. I'm wondering what test should/can be done to check if the chain is stretched and needs replacement.

chancecasey · 02-21-2007, 09:35 AM

Easiest test would be to buy a new one and stretch them out side by side and compare. If yours is the same length, just return the new one. If yours is measurably longer, toss it. Same can be said for the sprockets - if the old sprocket has the pockets pushed down more than the new one, or teeth look visibly different than the new one, replace it also. What's the mileage on the current chains/sprockets? My chains were noticeably stretched after 100K miles on my 3.6.

joetiii · joetiii's Garage

Well right now the timing chain is installed in the car. I'm planning on doing an in car pressure fed tensioner install. The engine is an 82 3.0 that was rebuilt to stock configuration 5 years and 6000 miles ago. The rebuild sheets I got from the PO didn't show tensioner upgrade, new sprockets or a chain so I'm figuring them to be original equipment.

Last time I ran long and hard back in November ( car is put away from the snow right now), I got this nasty metal on metal sound almost like metal slapping so that's why I think I got a tensioner problem and maybe a elongated chain. I guess the best way is to open up the cover and see what the ramps look like.

2.7RACER · 02-22-2007, 01:20 PM

Here are pics of a new chain and an old worn out chain.

Notice how close the pivot arm is to the top of the timing case with the worn out chain as compared to new chain.
As long as you have the motor out and apart replace the chain.
Replace the sprockets if they are visibly worn. Replacing the drive sprocket on the intermediate shaft will require splitting the case.

joetiii · joetiii's Garage

ahhhhh excellent photo. I will make a visible check when I crack her open.

safe · safe's Garage

You know its a crap shoot replacing the chains?
You need new sprockets also to be sure and the inner sprocket is kind of hard to change....
Do a search on chaning cam chains and look for posts from Gunter.

im4duke · 02-23-2007, 11:41 AM

What would you say for these chains?

2.7RACER · 02-23-2007, 04:24 PM

Looks like you have the motor out. The chains are over 50% worn out. This is one of those while you're in there, might as well change 'em.

im4duke · 02-23-2007, 05:58 PM

Quote:

Originally posted by 2.7RACER
Looks like you have the motor out. The chains are over 50% worn out. This is one of those while you're in there, might as well change 'em.

It's out and being completely rebuilt. Surprised though as it only has 39k miles.

2.7RACER · 02-23-2007, 06:50 PM

Completely rebuilt with only 39K miles? What's going on?

im4duke · 02-23-2007, 07:40 PM

3.3L Ruf modified turbo. Ruf's nice manual boost control b/w seats. 3-5 previous owners. 37k on the clock when I got her. 80% leakage on #4.

I really want to drive her and want to start with a clean slate. I think I get equal enjoyment out of tinkering as I do driving....though I seem to spend more time tinkering on things than actually use them. Must be the ex-engineer in me. I think I'm in good company on this forum.

88911coupe · 07-31-2008, 09:38 AM

Just to get the general concensus here...my '88 3.2 (160k) is going back together and the chains, sprokets, et al look to be in extremely good shape. There was plenty of space between the case and the end of the "arm" indicating minimal wear, maybe due to frequent oil changes. Anyway, I plan to reuse the chain since a new chain seems to be a "no-no"...correct? I don't want to have to replace everything else involved with the chains since it all looks to be in such excellent condition. Is this stupid?

Eagledriver · 07-31-2008, 10:10 AM

Buck,

I'd keep your old chains but replace the plastic chain guides (ramps).

-Andy

aws · 07-31-2008, 10:23 AM

Please be aware that whether the case spigot deck and cylinder head sealing surface has been machined will affect the tensioner piston height. On mag case engines that have been rebuilt several times and those surfaces machined you will often be at the end of the tensioner range even with new chains. I have never found a satisfactory method to check chains for stretch on the bench. I will say that new chains wear and stretch more when new and then remain a constant length for many miles. I would find the new chains loose on race engines after just a few hours and have to adjust the mechanical tensioners, if they were used they would not need the adjustment. New sprockets also tend to exacerbate this problem.

aws

88911coupe · 07-31-2008, 11:20 AM

Andy, thanks, have new guides (and a lot of other stuff) from our host waiting to go into the engine.